Shift control system of automatic transmission and method thereof

ABSTRACT

A shift control system of an automatic transmission and a method thereof include controlling the off-going and on-coming clutches according to hydraulic pressures of the off-going and on-coming clutches calculated based on a flare amount when a flare occurs, controlling the on-coming clutch according to hydraulic pressure of the on-coming clutch calculated based on a shifting time interval when the flare does not occur and the shifting time interval is smaller than or equal to a predetermined time interval, and controlling the off-going and on-coming clutches according to hydraulic pressures of the off-going and on-coming clutches calculated based on an excess rate of change of a turbine speed when the shifting time interval is larger than a predetermined time interval.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Divisional of U.S. patent application Ser. No.11/509,263, filed Aug. 24, 2006, which claims priority to and thebenefit of Korean Patent Application No. 10-2005-0124946 filed in theKorean Intellectual Property Office on Dec. 17, 2005, the entirecontents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a shift control system of an automatictransmission and a method thereof.

More particularly, the present invention relates to a shift controlsystem of an automatic transmission and a method thereof that controlshydraulic pressures of an off-going clutch and an on-coming clutchduring shifting.

2. Description of the Related Art

In an automatic transmission provided with a clutch-to-clutch shiftsystem, which is an independent shift system, when up-shifting ordown-shifting a shift speed, an off-going clutch is controlled not bycontrolling a hydraulic pressure of the off-going clutch, but bycontrolling a time when the hydraulic pressure of the off-going clutchis released. After controlling the time when the pressure of theoff-going clutch is released, the hydraulic pressure is released withoutadditional control.

In such an automatic transmission, the hydraulic pressure of theoff-going clutch is determined when a hydraulic pressure of an on-comingclutch rises. However, if the hydraulic pressure of the off-going clutchis quickly released or the hydraulic pressure of the on-coming clutch isslowly applied, flare may occur.

In addition, if the hydraulic pressure of the off-going clutch is highin an up-shifting process, problems such as tie-up and deterioration ofride comfort may occur at the early stages of the shifting process.

The above information disclosed in this Background section is only forenhancement of understanding of the background of the invention andtherefore it may contain information that does not form the prior artthat is already known in this country to a person of ordinary skill inthe art.

BRIEF SUMMARY OF THE INVENTION

A shift control method of an automatic transmission according to anexemplary embodiment of the present invention includes detecting avehicle speed and a throttle opening, determining whether a shiftingcondition is satisfied based on the vehicle speed and the throttleopening, calculating a required shift speed based on the vehicle speedand the throttle opening from a shifting pattern map table if theshifting condition is satisfied, performing a shifting process based oncalculated hydraulic pressures of an off-going clutch and an on-comingclutch that are calculated correspondent to the required shift speedfrom a hydraulic pressure map table, determining whether a flare occursin the shifting process, calculating hydraulic pressures of theoff-going and on-coming clutches based on the flare amount from thehydraulic pressure map table if flare occurs, and/or controlling theoff-going and on-coming clutches according to the hydraulic pressuresthereof calculated based on the flare amount.

In addition, the hydraulic pressures of the off-going and on-comingclutches correspondent to the required shift speed may be updated in thehydraulic pressure map table according to the hydraulic pressures of theoff-going and on-coming clutches calculated based on the flare amount.

The shift control method of the automatic transmission may furtherinclude if the flare does not occur, determining whether a shifting timeinterval is smaller than a predetermined time interval, calculating ahydraulic pressure of the on-coming clutch based on the shifting timeinterval from the hydraulic pressure map table if the shifting timeinterval is smaller than or equal to the predetermined time interval,and/or controlling the on-coming clutch according to the hydraulicpressure thereof calculated based on the shifting time interval.

The hydraulic pressure of the on-coming clutch correspondent to therequired shift speed may be updated in the hydraulic pressure map tableaccording to the hydraulic pressure of the on-coming clutch calculatedbased on the shifting time interval.

The shift control method of the automatic transmission may furtherinclude determining, if the shifting time interval is larger than thepredetermined time interval, whether the shifting process has begun,detecting a rate of change of a turbine speed during the shifting timeinterval if the shifting process has not begun, determining whether therate of change of the turbine speed is larger than a predeterminedvalue, calculating hydraulic pressures of off-going and on-comingclutches based on an excess rate of change of the turbine speed from thehydraulic pressure map table if the rate of change of the turbine speedis larger than the predetermined value, and/or controlling the off-goingand on-coming clutches according to the hydraulic pressures thereofcalculated based on the excess rate of change of the turbine speed.

In addition, the hydraulic pressures of the off-going and on-comingclutches correspondent to the required shift speed may be updated in thehydraulic pressure map table according to the hydraulic pressures of theoff-going and on-coming clutches calculated based on the excess rate ofchange of the turbine speed.

If the shifting process has begun, or the rate of change of the turbinespeed is smaller than or equal to the predetermined value, the off-goingand on-coming clutches are controlled according to the hydraulicpressures thereof calculated correspondent to the required shift speed.

A shift control system of an automatic transmission according to anexemplary embodiment of the present invention includes a vehicle speeddetector for detecting a vehicle speed and generating a signalcorresponding thereto, a throttle opening detector for detecting athrottle opening and generating a signal corresponding thereto, anengine speed detector for detecting an engine speed and generating asignal corresponding thereto, a turbine speed detector for detecting aturbine speed and generating a signal corresponding thereto, a shiftcontrol module for calculating hydraulic pressures of an off-goingclutch and an on-coming clutch and generating corresponding signals, theshift control module being electrically connected to the vehicle speeddetector, the throttle opening detector, the engine speed detector, andthe turbine speed detector, and/or a plurality of solenoid valves forreceiving the signals of the shift control module and operating theoff-going and on-coming clutches according thereto.

The shift control module may store a shift pattern map table forcalculating a required shift speed based on the vehicle speed and thethrottle opening, and/or a hydraulic pressure map table for calculatingthe hydraulic pressures of the off-going and on-coming clutches based onthe required shift speed, a flare amount, a shifting time interval, andan excess rate of change of a turbine speed.

The shift control module may be programmed to execute a shift controlincluding detecting a vehicle speed and a throttle opening, determiningwhether a shifting condition is satisfied based on the vehicle speed andthe throttle opening, calculating a required shift speed based on thevehicle speed and the throttle opening from a shifting pattern map tableif the shifting condition is satisfied, performing a shifting processaccording to hydraulic pressures of an off-going clutch and an on-comingclutch that are calculated correspondent to the required shift speedfrom a hydraulic pressure map table, determining whether a flare occursin the shifting process, calculating hydraulic pressures of theoff-going and on-coming clutches based on the flare amount from thehydraulic pressure map table if flare occurs, and/or controlling theoff-going and on-coming clutches according to the hydraulic pressuresthereof calculated based on the flare amount.

In addition, the hydraulic pressures of the off-going and on-comingclutches correspondent to the required shift speed may be updated in thehydraulic pressure map table according to the hydraulic pressures of theoff-going and on-coming clutches calculated based on the flare amount.

The shift control may further include determining, if flare does notoccur, whether a shifting time interval is smaller than a predeterminedtime interval, calculating a hydraulic pressure of the on-coming clutchbased on the shifting time interval from the hydraulic pressure maptable when the shifting time interval is smaller than or equal to thepredetermined time interval, and/or controlling the on-coming clutchaccording to the hydraulic pressure thereof calculated based on theshifting time interval.

In addition, the hydraulic pressure of the on-coming clutchcorrespondent to the required shift speed may be modified in thehydraulic pressure map table according to the hydraulic pressure of theon-coming clutch calculated based on the shifting time interval.

The shift control may further include determining, if the shifting timeinterval is larger than the predetermined time interval, whether theshifting process has begun, detecting a rate of change of a turbinespeed during the shifting time interval if the shifting process has notbegun, determining whether the rate of change of the turbine speed islarger than a predetermined value, calculating hydraulic pressures ofoff-going and on-coming clutches based on an excess rate of change ofthe turbine speed from the hydraulic pressure map table when the rate ofchange of the turbine speed is larger than the predetermined value,and/or controlling the off-going and on-coming clutches according to thehydraulic pressures thereof calculated based on the excess rate ofchange of the turbine speed.

In addition, the hydraulic pressures of the off-going and on-comingclutches correspondent to the required shift speed may be updated in thehydraulic pressure map table according to the hydraulic pressures of theoff-going and on-coming clutches calculated based on the excess rate ofchange of the turbine speed.

If the shifting process has begun, or the rate of change of the turbinespeed is smaller than or equal to the predetermined value, the off-goingand on-coming clutches may be controlled according to the hydraulicpressures thereof calculated correspondent to the required shift speed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a shift control system of an automatictransmission according to an exemplary embodiment of the presentinvention; and

FIG. 2 is a flowchart of a shift control method of an automatictransmission according to an exemplary embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

Exemplary embodiments of the present invention will hereinafter bedescribed in detail with reference to the accompanying drawings.

A shift control system according to various embodiments of the presentinvention includes a vehicle speed detector 101 mounted on an outputshaft of a transmission so as to detect a rotation speed of the outputshaft and to generate a signal corresponding thereto.

The shift control system also includes a throttle opening detector 103,which detects a throttle opening, which corresponds to the amount ofdepression of the accelerator pedal, and generates a signalcorresponding thereto.

The shift control system also includes a engine speed detector 105,which detects an input torque of the transmission according to anangular displacement of a crank shaft and generates a signalcorresponding thereto.

The shift control system also includes a turbine speed detector 107,which detects an output torque of the transmission and generates asignal corresponding thereto.

The shift control system also includes a shift control module 109, whichmay comprise a processor, memory, and associated hardware, software,and/or firmware as bay be selected and programmed by a person ofordinary skill in the art based on the teachings of the presentinvention. In various embodiments, shift control module 109 may compriseone or more processors activated by a program that performs theinventive method, which will be described in detail below. The shiftcontrol module 109 stores a shift pattern map table 113 and a hydraulicpressure map table 115. The shift control module 109 is electricallyconnected to the vehicle speed detector 101, the throttle openingdetector 103, the engine speed detector 105, and the turbine speeddetector 107, and receives signals of the vehicle speed, the throttleopening, the engine speed, and the turbine speed. In addition, the shiftcontrol module 109 calculates hydraulic pressures of an off-going clutchand an on-coming clutch, and generates signals corresponding thereto.

The shift control module 109 respectively receives the signals of thevehicle speed and the throttle opening from the vehicle speed detector101 and the throttle opening detector 103, and calculates a requiredshift speed based on the vehicle speed and the throttle opening from theshift pattern map table 113.

The shift control module 109 then calculates the hydraulic pressures ofthe off-going and on-coming clutches from the hydraulic pressure maptable 115 according to the required shift speed calculated from theshift pattern map table 113. The shift control module 109 generatessignals of the hydraulic pressures of the off-going and on-comingclutches, and transmits the signals to a plurality of actuators such assolenoid valves 111.

In addition, if a flare occurs, the shift control module 109 calculateshydraulic pressures of the off-going and on-coming clutches from thehydraulic pressure map table 115 based on the flare amount. The shiftcontrol module 109 generates corresponding signals and transmits thecorresponding signals to the plurality of solenoid valves 111. Afterthat, the hydraulic pressures of the off-going and on-coming clutchescorrespondent to the required shift speed are updated in the hydraulicpressure map table 115 according to the hydraulic pressures of theoff-going and on-coming clutches calculated based on the flare amount inthe map table 115.

If flare does not occur, the shift control module 109 detects a shiftingtime interval, defined as a required time from the time when theshifting condition is satisfied to the time when the shifting processactually begins. The shift control module 109 then determines whetherthe shifting time interval is smaller than a predetermined timeinterval. If the shifting time interval is smaller than or equal to thepredetermined time interval, the shift control module 109 calculates thehydraulic pressure of the on-coming clutch from the hydraulic pressuremap table 115 based on the shifting time interval and transmitscorresponding signals to the plurality of solenoid valves 111. Afterthat, the hydraulic pressure of the on-coming clutch correspondent tothe required shift speed is updated in the hydraulic pressure map table115 according to the hydraulic pressure of the on-coming clutchcalculated based on the shifting time interval.

If the shifting time interval is larger than the predetermined timeinterval, the shift control module 109 detects a rate of change of aturbine speed during the shifting time interval, and compares the rateof change of the turbine speed with a predetermined value.

If the rate of change of the turbine speed is larger than thepredetermined value, the shift control module 109 calculates thehydraulic pressures of the off-going and on-coming clutches from thehydraulic pressure map table 115 based on an excess rate of change ofthe turbine speed, and transmits corresponding signals to the pluralityof solenoid valves 111, thus preventing tie-up. After that, thehydraulic pressures of the off-going and on-coming clutchescorrespondent to the required shift speed are updated in the hydraulicpressure map table 115 according to the hydraulic pressures of theoff-going and on-coming clutches calculated based on the excess rate ofchange of the turbine speed.

The plurality of solenoid valves 111 are mounted on a valve body of thetransmission, and actuate the off-going and on-coming clutches byapplying the hydraulic pressures thereto or by releasing the hydraulicpressures therefrom. The plurality of solenoid valves 111 are operatedaccording to the signals transmitted from the shift control module 109.

A shift control method of an automatic transmission according to variousembodiments of the present invention will hereinafter be described indetail with reference to the accompanying drawings.

As shown in FIG. 2, when the vehicle is running, the shift controlmodule 109 receives the signal of the vehicle speed from the vehiclespeed detector 101 and the signal of the throttle opening from thethrottle opening detector 103 at step S100. In this state, the shiftcontrol module 109 determines whether the shifting condition issatisfied based on the vehicle speed and the throttle opening at stepS105.

If the shifting condition is not satisfied, the current running state ismaintained. If the shifting condition is satisfied, the shift controlmodule 109 calculates the required shift speed from the shift patternmap table 113 according to the vehicle speed and the throttle opening atstep S110, and calculates the hydraulic pressures of the off-going andon-coming clutches correspondent to the required shift speed at stepS115. After that, the shift control module 109 transmits control signalsto the plurality of solenoid valves 111, and the plurality of solenoidvalves 111 control the shifting process by applying the hydraulicpressures to the off-going and on-coming clutches or by releasing thehydraulic pressures from the off-going and on-coming clutches at stepS120.

In this case, the shift control module 109 determines whether flareoccurs at step S125. The flare occurs when a hydraulic pressure isquickly released from the off-going clutch or a hydraulic pressure isslowly applied to the on-coming clutch.

If the flare occurs, the hydraulic pressures of the off-going andon-coming clutches are calculated from the hydraulic pressure map table115 based on the flare amount, and the off-going and on-coming clutchesare controlled at step S130 according to the hydraulic pressures thereofcalculated based on the flare amount.

In addition, the hydraulic pressures of the off-going and on-comingclutches correspondent to the required shift speed are modified in thehydraulic pressure map table 115 according to the hydraulic pressures ofthe off-going and on-coming clutches calculated based on the flareamount.

However, if the flare does not occur, the shift control module 109determines whether the shifting time interval is smaller than thepredetermined time interval at step S135.

If the shifting time interval is smaller than or equal to thepredetermined time interval, the hydraulic pressure of the on-comingclutch is calculated from the hydraulic pressure map table 115 based onthe shifting time interval, and the on-coming clutch is controlled atstep S140 according to the hydraulic pressure thereof calculated basedon the shifting time interval.

In addition, the hydraulic pressure of the on-coming clutchcorrespondent to the required shift speed is modified in the hydraulicpressure map table 115 according to the hydraulic pressure of theon-coming clutch calculated based on the shifting time interval.

However, if the shifting time interval is larger than the predeterminedtime interval, the shift control module 109 determines at step S145whether the shifting process has actually begun.

If the shifting process has not begun, the off-going and on-comingclutches are controlled according to the hydraulic pressures thereofcalculated based on the required shift speed.

If the shifting process has begun, the shift control module 109 receivesthe signal of the turbine speed from the turbine speed detector 107 andcalculates the rate of change of the turbine speed dN(t)/dt, where N isthe turbine speed in rpm. After that, the shift control module 109determines at step S 150 whether the rate of change of the turbine speedis larger than a predetermined value.

If the rate of change of the turbine speed dN(t)/dt is smaller than orequal to the predetermined value, the off-going and on-coming clutchesare controlled according to the hydraulic pressures thereof calculatedbased on the required shift speed.

If the rate of change of the turbine speed dN(t)/dt is larger than thepredetermined value, the excess rate of change of the turbine speeddN(t)/dt is calculated at step S155. The hydraulic pressures of theoff-going and on-coming clutches are calculated based on the excess rateof change of the turbine speed dN(t)/dt from the hydraulic pressure maptable 115 at step S160. The off-going and on-coming clutches are thencontrolled according to the hydraulic pressures thereof calculated basedon the excess rate of change of the turbine speed at step S165.

In addition, the hydraulic pressures of the off-going and on-comingclutches correspondent to the required shift speed are modified in thehydraulic pressure map table 115 according to the hydraulic pressures ofthe off-going and on-coming clutches calculated based on the excess rateof change of the turbine speed.

While this invention has been described in connection with what ispresently considered to be practical exemplary embodiments, it is to beunderstood that the invention is not limited to the disclosedembodiments, but, on the contrary, is intended to cover variousmodifications and equivalent arrangements included within the spirit andscope of the appended claims.

As described above, the hydraulic pressures of the off-going andon-coming clutches are calculated in an early stage of the shiftingprocess according to the present invention. Thus, the present inventionhas advantages of minimizing both flare and tie-up, and of enhancing ashift feel.

1. A shift control system of an automatic transmission, comprising: avehicle speed detector for detecting a vehicle speed and generating asignal corresponding thereto; a throttle opening detector for detectinga throttle opening and generating a signal corresponding thereto; anengine speed detector for detecting an engine speed and generating asignal corresponding thereto; a turbine speed detector for detecting aturbine speed and generating a signal corresponding thereto; a shiftcontrol module for calculating hydraulic pressures of an off-goingclutch and an on-coming clutch and generating corresponding signals, theshift control module being electrically connected to the vehicle speeddetector, the throttle opening detector, the engine speed detector, andthe turbine speed detector; and a plurality of actuators for receivingthe signals of the shift control module and operating the off-going andon-coming clutches according thereto; wherein the shift control modulecomprises: a shifting pattern map table for calculating a required shiftspeed based on the vehicle speed and the throttle opening; and ahydraulic pressure map table for calculating the hydraulic pressuresbased on the required shift speed, a flare amount, a shifting timeinterval, and an excess rate of change of the turbine speed; and whereinthe shift control module is programmed to execute a shift controlcomprising: detecting the vehicle speed and the throttle opening;determining whether a shifting condition is satisfied based on thevehicle speed and the throttle opening; calculating a required shiftspeed based on the vehicle speed and the throttle opening from theshifting pattern map table when the shifting condition is satisfied;performing a shifting process according to first hydraulic pressures ofthe off-going and on-coming clutches; determining whether a flare occursin the shifting process; calculating second hydraulic pressures of theoff-going and on-coming clutches based on the flare amount from thehydraulic pressure map table if the flare occurs; and controlling theoff-going and on-coming clutches according to the second hydraulicpressures; determining, if the flare does not occur, whether a shiftingtime interval is smaller than a predetermined time interval; calculatinga third hydraulic pressure of the on-coming clutch based on the shiftingtime interval from the hydraulic pressure map table if the shifting timeinterval is smaller than or equal to the predetermined time interval;controlling the on-coming clutch according to the third hydraulicpressure; determining, if the shifting time interval is larger than thepredetermined time interval, whether the shifting process has begun;detecting a rate of change of a turbine speed during the shifting timeinterval if the shifting process has begun; determining whether the rateof change of the turbine speed is larger than a predetermined value;calculating fourth hydraulic pressures of the off-going and on-comingclutches based on the excess rate of change of the turbine speed fromthe hydraulic pressure map table if the rate of change of the turbinespeed is larger than the predetermined value; and controlling theoff-going and on-coming clutches according to the fourth hydraulicpressures.
 2. The system of claim 1, wherein the first hydraulicpressures are updated in the hydraulic pressure map table according tothe fourth hydraulic pressures.
 3. The system of claim 1, wherein theoff-going and on-coming clutches are controlled according to the firsthydraulic pressures if the shifting process has begun.
 4. The system ofclaim 1, wherein the off-going and on-coming clutches are controlledaccording to the first hydraulic pressures if the rate of change of theturbine speed is smaller than or equal to the predetermined value. 5.The system of claim 1, wherein the first hydraulic pressures are updatedin the hydraulic pressure map table according to the second hydraulicpressures.
 6. The system of claim 1, wherein the first on-coming clutchhydraulic pressure is updated in the hydraulic pressure map tableaccording to the third hydraulic pressure.